A matrix sensor is made up of an assembly of cells disposed in row and in column. In its most common form of operation, these cells are sequentially scanned in order to measure the presence of points of contact or points of pressure. Such multicontact tactile sensors and their analysis method are described, for example, in documents EP 1 719 047 or EP 2 142 980. In document EP 2 142 980, the cells are made up of a material acting as a diode.
Likewise, the present invention concerns tactile sensors using a matrix of active cells, such as those of TFT type (Thin Film Transistor), of photodiode type, which can be directly integrated in the matrix of an LCD screen (Liquid Crystal Display), or even of piezo-electric type.
In document EP 1 719 047, the matrix tactile sensor is made up of a matrix array of strip conductors disposed along rows and columns, cells being thus defined at each intersection of the rows and the columns of the matrix array.
The acquisition of data is done by sequentially scanning each cell of the matrix array, that is, by successively energizing each row of the matrix array and measuring, for each row energized, and at each column successively, an electrical characteristic representative of an impedance level.
The set of these electrical characteristics representative of a level of impedance of each cell is then memorized.
By virtue of this sequential scanning of the cells, it is possible to detect simultaneously several zones of contact on the tactile sensor during each scanning phase.
The data measured, and especially the level of impedance of each cell, are recorded.
Due to the recording of the set of data acquired in each scanning phase, it is necessary to have an electronic memory of large size, thus increasing the manufacturing cost of the tactile sensor.
Furthermore, in the context of a tactile sensor having great sensitivity and possibly containing several thousand cells, depending on the size of its tactile surface, the set of data acquired for each cell is then analyzed to determine surrounding zones, that is, encompassing several neighboring cells in the matrix array and thus corresponding to a single contact or a point of pressure on the tactile surface of the sensor.
This step of determination of surrounding zones thus requires an analysis of the matrix image of the sensor, obtained during the sequential scanning phase, and it induces a latency period in the response of the sensor.
This step of analysis of the set of data stored in memory takes longer to implement as the matrix image stored in memory is more complex. When this analysis step is realized in parallel with a scanning phase, it is necessary to provide a buffer memory size that is sufficient to record at least two matrix images of the sensor at the same time.